1. Field of the Invention
The present invention relates to a semiconductor light emitting element and a manufacturing method thereof.
2. Description of the Related Art
In recent years, an increase in the size of semiconductor light emitting elements has been required. However, when the size of the semiconductor light emitting element is increased, a defective region is more likely to be generated in a semiconductor laminate of the element. A semiconductor light emitting element having a defective region in a part of the semiconductor laminate is determined to be defective, even when most of the regions in the semiconductor laminate are acceptable. Therefore, the number of large-sized semiconductor light emitting elements that can be formed from one piece of wafer is decreased, which results in poor yield. Further, the acceptable regions are disadvantageously wasted.
For the purpose of effectively using the acceptable regions, a method may be used which involves connecting a plurality of small-sized elements to thereby form a large-sized chip (see, for example, JP-A-2010-192837). In this method, a large-sized chip is subjected to dicing so as not to contain defective small-sized elements, while acceptable small-sized elements remaining together with the defective small-sized elements are subjected to dicing to produce medium-sized chips. Thus, the number of wasted acceptable regions is reduced, which can improve the yield of the large and medium-sized chips.
A laminated semiconductor light emitting element may be formed by growing a semiconductor laminate on a growth substrate, bonding the semiconductor laminate to a conductive support substrate, and then removing the growth substrate (see, for example, JP-A-2004-266240 and International Publication No. WO 2003/065464 pamphlet).
Another problem caused by increasing the size of the semiconductor light emitting element is warpage. In case of a laminated semiconductor light emitting element, warpage is caused by the difference in a thermal expansion coefficient between the growth substrate and the semiconductor element, and the warpage remains in the semiconductor laminate even when the growth substrate is removed.
Still another problem caused by increasing the size of the semiconductor light emitting element is the reduction in efficiency of light extraction. A part of light generated by an active layer of the semiconductor laminate is laterally transmitted, while being reflected by the upper and lower surfaces of the semiconductor laminate. The light reaching the side of the semiconductor laminate is emitted toward the outside of the element. In a large-sized semiconductor light emitting element, the average distance traveled by the light until it reaches the side of the semiconductor light emitting element becomes long, which increases the number of reflections of the light before it is emitted from the light emitting element. When the light is reflected (in particular, reflected off an interface between the substrate and the semiconductor laminate), the light is absorbed. Thus, as the number of reflections of the light is increased, the intensity of the light emitted from the light emitting element is reduced.
In a laminated semiconductor light emitting element formed using a semiconductor laminate containing a nitride, a distance (thickness of a p-type semiconductor layer) between the substrate and the active layer is short. Therefore, light may be repeatedly reflected before being emitted from the light emitting element. Such repeatedly reflected light tends to be absorbed at the interface between the substrate and the semiconductor laminate. Thus, there is a need for a large-sized laminated semiconductor light emitting element having improved light extraction efficiency.